1. Field of the Invention
The invention relates to a thin speaker structure, particularly to a speaker body that can improve the rigidity of a membrane and suppress the segmental vibration of the membrane.
2. Description of the Related Art
The traditional moving-coil speaker is mainly rounded. A conventional round speaker 70 as shown in FIG. 1A includes a round voice coil and a magnetic circuit element 72 arranged below a membrane 71. The membrane 71 and the voice coil are proportional concentric circles. When the membrane 71 is axially moved up and down by the voice coil, each point affected by forces on the membrane 71 is the same, resulting in the best sound quality.
However, when the consumer electronic products are required to be thin and light, the space provided for the speaker is very limited. Sometimes, the position of the speaker is often set in a corner in order to accommodate the demand for ultra-thin consumer electronic products such as mobile phones, tablet computers or notebook computers (NB) with rectangular appearances. Also, the speaker is required to meet the demand of good sound quality and volume and thus many thin speakers are produced in non-circular shapes, as shown in FIGS. 1B and 1C, the speaker structure is set into an elliptic shape.
In FIG. 1B, a conventional elliptic speaker 80, a normal speaker body using in the consumer electronic products, includes an elliptic membrane 81 with a body and a surrounding, an elliptic voice coil 81 arranged below the membrane 81, and an elliptic magnetic circuit element 82. The membrane 81 has a center portion 811 smaller than the voice coil and is set to be in an elliptic or polygonal shape. Comparing to the round structure, when the area of the membrane 81 of the elliptic or polygonal structure is increased, the volume increased and the bass response is better. But the disadvantage is that the voice coil and the magnetic circuit element 82 are ellipses and thus the material costs increase a lot and the production process are more complicated.
In order to solve the costs and production process problems of the elliptic speaker 80, a conventional elliptic speaker 90 as shown in FIG. 1C provides a round center portion 911 of a membrane 91, a round voice coil, and a round magnetic circuit element 92 wherein a diameter of the voice coil is longer or equal than or to a diameter of the center portion 911.
The above structure has advantage of reducing the material costs and production process. Due to the smaller magnetic circuit element 92, there are more sound chamber spaces behind the speaker for increasing resonated spaces and enhancing the bass and volume. However, the round voice coil and the elliptic membrane 91 leads to different forces on the short side and long side of the membrane 91 when the voice coil vibrates; so that the long edges is easy to generate a radial segmental vibration resulting in poor performance in middle level frequency (MLF), and distortion. The MLF is one of the most sensitive areas of sound for humans, so poor MLF performance will affect the evaluation of consumer for speakers. Moreover, this structure usually provides a concave membrane in order to reduce the above MLF problems and reduce the segmental vibration movement of the membrane but this result leads to an overall increase in the thickness of the speaker, not meeting the needs of slim consumer electronic products.
In view of the aforementioned, problems, the inventor of the present invention conducted researches and experiments and developed a thin speaker structure to overcome the problems of the prior art.